There was a time that the Windows Phone partner was actively working on an Android Lumia smartphone, according to The New York Times

From Techradar:

According to the report, the long-desired combination of Nokia's hardware with Google's operating system was being handled by a team within the company that had Android running on a Lumia handset. Worst of all for those who have had this if only fantasy, it wouldn't have been all that hard for the company to start using Google's interface and apps on Nokia's phone. Porting Android to the Nokia Lumia was not a Herculean task, according to the paper's sources.